Question 1

Sieve plates:

Accepted Answer

Sieve plates are modified cell walls that connect sieve elements, allowing for the movement of phloem sap through the phloem cells.

Question 2

Under what circumstances are leaves "sinks" for carbohydrates delivered by phloem?

Accepted Answer

Young leaves are considered "sinks" for carbohydrates because they are still growing and require energy for development. They do not yet photosynthesize at a rate sufficient to meet their energy needs, so they rely on carbohydrates transported from other parts of the plant.

Question 3

At the "source" end of the phloem, sugar loaded into the phloem draws water into the sieve tubes by osmosis, raising the pressure. What happens to the water at the sink end?

Accepted Answer

The answer of At the "source" end of the phloem,...

Question 4

Which of the following are NOT transported in phloem?

Accepted Answer

Large starch molecules are not transported in phloem.

Question 5

A sieve element does NOT contain which of the following?

Accepted Answer

Sieve elements are specialized plant cells that form the phloem tissue and are responsible for the transportation of organic molecules throughout the plant. They lack a nucleus, making them unable to carry out protein synthesis and other cellular functions that require a nucleus. Therefore, the best choice for the option that a sieve element does NOT contain is E, the nucleus.

Question 6

The status of a tissue as source or sink may change depending on the growth and development of that tissue as well as tissues located elsewhere in the plant.

Accepted Answer

The status of a tissue as source or sink depends on the current demand and supply of nutrients and carbohydrates in the plant, which is influenced by the growth and development of that tissue as well as other tissues in the plant. Therefore, it can change over time.

Question 7

Carbohydrates are stored in the roots, but they may also be released into the surrounding soil, where they feed the microbial community.

Accepted Answer

Carbohydrates produced by plants can be stored in the roots or released into the soil to feed the microbial community. This process is known as rhizodeposition and helps to support soil health and nutrient cycling.

Question 8

A botanist extracts the contents of a plant's vasculature. Upon analysis, she finds that these contents contain both ions and RNA. The botanist likely targeted a:

Accepted Answer

Sieve tubes, part of the phloem in plants, are responsible for transporting sugars and other metabolic products. Unlike tracheids and vessels, which are part of the xylem and mainly transport water and minerals, sieve tubes can also transport RNA and proteins, explaining the presence of both ions and RNA in the extracted contents.

Question 9

Why may young leaves that are just emerging from the bud be considered "sinks" for phloem transport?

Accepted Answer

Young leaves that are just emerging from the bud are still growing and developing, so they require more carbohydrates than they are producing through photosynthesis. Therefore, they are considered "sinks" for phloem transport, as they consume more carbohydrates than they produce. Once the leaves mature and begin producing more carbohydrates through photosynthesis, they become "sources" for phloem transport.

Question 10

A companion cell supports a sieve element by performing specific cellular processes.

Accepted Answer

A companion cell is closely associated with a sieve element and provides metabolic support, such as energy and nutrient supply, to the sieve element. It also helps to regulate the transport activities of the sieve element to maintain the proper functioning of the phloem.

Question 11

In order to conserve H₂O, land plants will close stomata to minimize transpiration, but closing stomata lowers CO₂ concentration in the leaf. Drought thus _____ because _____.

Accepted Answer

When plants close stomata to minimize transpiration during drought, the concentration of CO₂O in the leaf decreases. CO₂O is necessary in the process of photosynthesis, and when it is limited, the rate of photosynthesis decreases. The decrease in CO2 availability also leads to an increase in photorespiration, which further reduces the rate of photosynthesis. Thus, drought lowers photosynthesis and increases photorespiration.

Question 12

Vascular plants store most carbohydrate reserves as:

Accepted Answer

Vascular plants store most carbohydrate reserves as starch in specialized structures such as roots, tubers, and seeds. Glycogen is primarily stored in animal tissues, while sucrose and glucose are used for transport within plants but not long-term storage. Lipids can also be used for energy storage but are not considered carbohydrates.

Question 13

Which of the following is TRUE of transport in phloem?

Accepted Answer

Transport in phloem is driven by the pressure gradient created by the loading of sugars and other compounds into the phloem at the source (usually leaves) and unloading at the sink (usually growing or storage tissues). This loading and unloading creates a pressure gradient that drives the flow of materials in the phloem. This pressure is called turgor pressure.

Question 14

Roots elongate continuously in order to:

Accepted Answer

Roots elongate continuously in order to mine new regions of soil for nutrients. This helps the plant to absorb water and nutrients from a larger area of soil, increasing its chances of survival and growth. Option B is incorrect as roots do not act as a carbohydrate sink. Option C is incorrect as O₂ is not a known nutrient required by plants.

Question 15

Which of the following statements is FALSE regarding the relationship of xylem and phloem?

Accepted Answer

Phloem cells are actually alive at maturity and are kept alive through the processes of companion cell action, active pumping of sucrose, and intracellular signaling. Xylem cells, on the other hand, are typically dead at maturity and function by simple physical processes such as capillary action and evaporation.

Question 16

A benefit of starch being the storage molecule in plants is that starch is easy for plants to move throughout the plant body.

Accepted Answer

Starch is not easily moved throughout the plant body; it is stored in specific locations like roots, seeds, and tubers because it is insoluble in water, making it difficult to transport. Plants convert starch back into glucose for transport.

Question 17

Which of the following statements is NOT true about phloem transport of sugars?

Accepted Answer

Removing sugars from phloem would decrease turgor pressure at the sink, as there would be less water flowing in to balance the solute concentration.

Question 18

Which of the following would be considered a carbohydrate sink in vascular plants?

Accepted Answer

The answer of Which of the following would be considered...

Question 19

Which of the following are NOT a correct match of cells and their function?

Accepted Answer

Parenchyma cells have a variety of functions such as photosynthesis, storage and secretion. They are not specifically involved in the transport of water.

Question 20

Xylem transports _____, whereas phloem transports _____.

Accepted Answer

Xylem is responsible for transporting water and minerals from the roots to the rest of the plant, while phloem is responsible for transporting sugars (produced during photosynthesis) from the leaves to the rest of the plant, including the roots. Therefore, B is the correct choice as it correctly identifies the substances transported by xylem and phloem.

Quiz 29: Plant Structure and Function: Moving Photosynthesis Onto Land

Sieve plates:

Under what circumstances are leaves "sinks" for carbohydrates delivered by phloem?

At the "source" end of the phloem, sugar loaded into the phloem draws water into the sieve tubes by osmosis, raising the pressure. What happens to the water at the sink end?

Which of the following are NOT transported in phloem?

A sieve element does NOT contain which of the following?

The status of a tissue as source or sink may change depending on the growth and development of that tissue as well as tissues located elsewhere in the plant.

Carbohydrates are stored in the roots, but they may also be released into the surrounding soil, where they feed the microbial community.

A botanist extracts the contents of a plant's vasculature. Upon analysis, she finds that these contents contain both ions and RNA. The botanist likely targeted a:

Why may young leaves that are just emerging from the bud be considered "sinks" for phloem transport?

A companion cell supports a sieve element by performing specific cellular processes.

In order to conserve H₂O, land plants will close stomata to minimize transpiration, but closing stomata lowers CO₂ concentration in the leaf. Drought thus _ because _.

Vascular plants store most carbohydrate reserves as:

Which of the following is TRUE of transport in phloem?

Roots elongate continuously in order to:

Which of the following statements is FALSE regarding the relationship of xylem and phloem?

A benefit of starch being the storage molecule in plants is that starch is easy for plants to move throughout the plant body.

Which of the following statements is NOT true about phloem transport of sugars?

Which of the following would be considered a carbohydrate sink in vascular plants?

Which of the following are NOT a correct match of cells and their function?

Xylem transports _, whereas phloem transports _.

Quiz 29: Plant Structure and Function: Moving Photosynthesis Onto Land

Sieve plates:

Under what circumstances are leaves "sinks" for carbohydrates delivered by phloem?

At the "source" end of the phloem, sugar loaded into the phloem draws water into the sieve tubes by osmosis, raising the pressure. What happens to the water at the sink end?

Which of the following are NOT transported in phloem?

A sieve element does NOT contain which of the following?

The status of a tissue as source or sink may change depending on the growth and development of that tissue as well as tissues located elsewhere in the plant.

Carbohydrates are stored in the roots, but they may also be released into the surrounding soil, where they feed the microbial community.

A botanist extracts the contents of a plant's vasculature. Upon analysis, she finds that these contents contain both ions and RNA. The botanist likely targeted a:

Why may young leaves that are just emerging from the bud be considered "sinks" for phloem transport?

A companion cell supports a sieve element by performing specific cellular processes.

In order to conserve H2O, land plants will close stomata to minimize transpiration, but closing stomata lowers CO2 concentration in the leaf. Drought thus _____ because _____.

Vascular plants store most carbohydrate reserves as:

Which of the following is TRUE of transport in phloem?

Roots elongate continuously in order to:

Which of the following statements is FALSE regarding the relationship of xylem and phloem?

A benefit of starch being the storage molecule in plants is that starch is easy for plants to move throughout the plant body.

Which of the following statements is NOT true about phloem transport of sugars?

Which of the following would be considered a carbohydrate sink in vascular plants?

Which of the following are NOT a correct match of cells and their function?

Xylem transports _____, whereas phloem transports _____.

In order to conserve H₂O, land plants will close stomata to minimize transpiration, but closing stomata lowers CO₂ concentration in the leaf. Drought thus _ because _.

Xylem transports _, whereas phloem transports _.